Growth factors stimulate the activity of key glycolytic enzymes in isolated digestive gland cells from mussels (Mytilus galloprovincialis Lam.) through tyrosine kinase mediated signal transduction

Digestive gland cells isolated from mussels (Mytilus) have previously been demonstrated to respond to mam malian EGF with a cytosolic Ca2+ transient a nd stimulated DNA synthesis; both responses were mediated by activation:of tyrosine kinase receptors. The present study examines the mechanisms involv ed in further signal progression and possible targets of phosphorylation/de phosphorylation processes. The effects of EGF, IGF-I, and insulin on the ac tivity of two key glycolytic enzymes PFK (phosphofructokinase) and PK (pyru vate kinase) were evaluated. All the peptides tested induced a transient an d dose-dependent stimulation of the activity of both PFK and PK, which invo lved activation of MAPKs. Quantitative immunoelectron microscopy, utilizing monoclonal anti-phosphotyrosine antibodies, revealed that EGF induced a tr ansient increase in tyrosine phosphorylation. The results demonstrate that, in marine invertebrate cells, activation of tyrosine kinase membrane recep tors by growth factors triggers signal transduction pathways involving a ph osphorylative cascade similar to that of mammalian cells. Moreover, these d ata suggest that, in mussel cells, growth factors may play:a physiological role in the in vivo regulation of glucose-metabolism by modulating, through reversible phosphorylation, the activity of key glycolytic enzymes. (C) 19 99 Academic Press.